Many motor vehicle tires have a circumferential tread provided with a plurality of circumferential grooves that define ribs therebetween. Typically, generally lateral slots can be provided in the ribs to form a plurality of shaped blocks. These shaped blocks can be distributed along the tread according to a specific pattern. Sipes, which are generally narrow slits cut into the tread, can be provided in the shaped blocks to improve wet, snow, and ice traction of the tire.
Generally, a siping element or blade is provided in a vulcanization mold to form a sipe in the tread of a tire. The blade can be provided in the vulcanization mold in the following ways: 1) both ends of the blade can be connected to or in contact with one or more ribs in the mold; 2) one end of the blade can be connected to or in contact with an adjacent rib in the mold; or 3) neither end of the blade is connected to or in contact with a rib in the mold. In the second and third scenarios, where one or both ends of the blade are not connected to or in contact with a rib in the mold, the end(s) of the blades are left unsupported. These unsupported end(s) of the blade are subject to damage (e.g., bending or warping) during the vulcanization process due to the intense pressure and heat created in the vulcanization mold.
To prevent the unsupported end(s) of the blade from bending or warping during the vulcanization process, the blade is designed to withstand the pressure and heat created in the vulcanization mold. Several important blade design factors include blade material and thickness. Generally, by increasing the material strength and thickness of the blade, the unsupported end is strengthened and its ability to withstand the vulcanization process increases. Other blade design factors include the length and height of the blade provided in the mold. Generally, by decreasing the length and height of the blade, the strength of the unsupported end increases. Another blade design consideration is the effect of heat on the blades during the casting of the vulcanization mold (e.g., an aluminum vulcanization mold). For example, when an aluminum mold is cast, the heat generated from the molten aluminum can cause the blades to be re-heated, thereby weakening the heat-treated blades.
Blades currently used in the tire industry are typically constructed of heat-treated steel (e.g., stainless or other alloy) having a thickness of at least 0.030 inches. The unsupported ends of these blades are typically capable of withstanding the heat and pressure generated during the vulcanization process. Blades also vary in length and height depending on the desired tread pattern.